A tire curing press commonly contains upper and lower mold halves, each of which is fixedly mounted on a steam platen which supplies heat to the mold for curing the tire. One of the mold half (usually the lower mold half) and its associated platen are usually stationary while the other mold half (usually the upper) and its associated platen are usually vertically reciprocable between an open position in which the mold halves are apart and a closed position in which the mold halves are together.
A steam platen commonly has two horizontal surfaces, one of which (commonly called the mold side surface) is in abutting relationship with the mold half, the other of which (commonly called the bolster side surface) is in abutting relationship with a supporting structure, e.g., a base (in the lower half of the press) or a head (in the upper half of the press). These surfaces are the outside surfaces of respective spaced horizontal walls. A steam cavity is situated between these walls. Steam (usually superheated) is supplied to the steam cavity via a steam inlet port, and steam (typically saturated with some condensate) is removed from the steam cavity via a steam outlet port.
A problem with presently known platens is that the configuration of the steam cavity is such that there are dead spots where there is little or no steam flow. Steam flow tends to channel, i.e., to follow the path of least resistance. As a result, portions of the mold side surface, i.e., those portions above or below the steam channels, are heated to a greater extent than other portions of the mold side surface, i.e., those which are above or below the dead spots. This results in a non-uniform temperature on the mold side surface of the platen and in the mold half associated with the platen. This phenomenon occurs in both the upper and the lower steam platens and their associated mold halves. As a result, the tire is cured unevenly. Cure is faster at the hotter portions or "hot spots" of the mold halves, and slower at the cooler portions or "cold spots" of the mold halves. In order to cure all of the tire sufficiently, it is necessary to heat portions of the tire to a higher temperature than is desired, and in extreme situations this may actually result in overcure of those portions. Conversely, if one opts for a desired curing temperature at the hotter portions of the mold, there is a risk of undercure of those portions of the tire which are at positions corresponding to the cold spots of the mold halves and the associated platens.